Construction workers have among the highest rates of occupational injury, yet there are significant challenges in understanding their work exposures and the injuries associated with them for a number of reasons that are closely associated with they way they work. Construction workers are mobile, working for multiple contractors, which makes them difficult to enumerate. Their job sites are constantly changing as are the associated hazards. The work is often done by multiple trade groups on site with different responsibilities, different immediate supervisors, potentially different safety priorities and training requirements, and usually different compensation carriers. Yet the work of one group of workers has great potential to affect the health and safety of other workers. In recent years, the U.S. economy has supported much construction; consequently the construction trades have attracted Latino workers, presenting new challenges associated with language and cultural differences to the safety and health of workers. We propose to assess occupational injuries and hazards on a long-term commercial construction site in the Denver area with a diverse workforce. The study will take place through collaboration with the University of Colorado's rolling owner-controlled insurance plan. This arrangement provides a unique opportunity to enumerate time at risk among a variety of trade groups and to document their work injuries and the circumstances surrounding those events as well as the changing hazards associated with different stages of construction. Data will be collected through a combination of quantitative and qualitative methods which will allow both case-based and rate-based analyses. The result should be improved understanding of the injury experience of workers as well as the context in which injuries occur on complex construction projects, which will be useful for guiding prevention efforts. The proposed work will address a number of NIOSH's priorities, including surveillance methods, traumatic injury, construction workers, and special populations, specifically Latino construction workers.